Internally cooled spoke

ABSTRACT

A turbine engine includes a compressor section, a combustor section in fluid communication with the compressor section, a high pressure turbine in fluid communication with the combustor, a low pressure turbine in fluid communication with the high pressure turbine, and a mid-turbine frame located axially between the high pressure turbine and the low pressure turbine. The mid-turbine frame includes an outer frame case, an inner frame case, and a plurality of hollow spokes that distribute loads from the inner frame case to the outer frame case. The spokes are hollow to allow cooling airflow to be supplied through the spokes to the inner frame case.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.13/753,821, filed Jan. 20, 2013 and entitled “Internally Cooled Spoke”,which is a continuation of U.S. patent application Ser. No. 13/361,480,filed Jan. 30, 2012 and entitled “Internally Cooled Spoke”.

BACKGROUND

The present disclosure relates generally to a gas turbine engine, and inparticular to a mid-turbine frame (MTF) included in a gas turbineengine.

A mid-turbine frame (MTF) is positioned between a high pressure turbinestage and a low pressure turbine stage of a gas turbine engine. The MTFsupports one or more bearings and transfers bearing loads from an innerportion of the gas turbine engine to an outer engine frame. The MTF alsoserves to route air from the high pressure turbine stage to the lowpressure turbine stage.

SUMMARY

A turbine engine includes a compressor section, a combustor section influid communication with the compressor section, a high pressure turbinein fluid communication with the combustor, a low pressure turbine influid communication with the high pressure turbine, and a mid-turbineframe located axially between the high pressure turbine and the lowpressure turbine. The mid-turbine frame includes an outer frame case, aninner frame case, and a plurality of hollow spokes that distributebearing loads from the inner frame case to the outer frame case. Thespokes are hollow to allow cooling airflow to be supplied through thespokes to the inner frame case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a gas turbine engine according to anembodiment of the present invention.

FIG. 2 is a perspective view of a mid-turbine frame (MTF) located in thegas turbine engine according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of mid-turbine frame (MTF) taken alongline 3-3 of FIG. 4.

FIG. 4 is a cross-sectional view of mid-turbine frame (MFT) taken alongline 4-4 of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 is a schematic view of gas turbine engine 20 according to anembodiment of the present invention. Gas turbine engine 20 is disclosedherein as a two-spool turbofan that generally incorporates fan section22, compressor section 24, combustor section 26 and turbine section 28,although alternative turbofan designs may benefit from the presentinvention. Fan section 22 drives air along a bypass flowpath while thecompressor section 24 drives air along a core flowpath for compressionand communication into the combustor section 26, and then expansionthrough the turbine section 28.

The engine 20 generally includes low speed spool 30 and high speed spool32 mounted for rotation about an engine central longitudinal axis Arelative to an engine static structure 36 via several bearing systems38. It should be understood that various bearing systems 38 at variouslocations may alternatively or additionally be provided.

Low speed spool 30 generally includes inner shaft 40 that interconnectsa fan 42, low pressure compressor 44 and low pressure turbine 46. Innershaft 40 is connected to fan 42 through geared architecture 48 to drivefan 42 at a lower speed than low speed spool 30. High speed spool 32includes outer shaft 50 that interconnects high pressure compressor 52and high pressure turbine 54. Combustor 56 is arranged between highpressure compressor 52 and high pressure turbine 54. Mid-turbine frame57 of the engine static structure 36 is arranged axially between highpressure turbine 54 and low pressure turbine 46. Mid-turbine frame 57further supports bearing systems 38 in turbine section 28. Inner shaft40 and outer shaft 50 are concentric and rotate via bearing systems 38about the engine central longitudinal axis A which is collinear withtheir longitudinal axes.

The core airflow is compressed by low pressure compressor 44 and then byhigh pressure compressor 52, mixed and burned with fuel in combustor 56,then expanded over high pressure turbine 54 and low pressure turbine 46.Combustor 56 is therefore in fluid communication with the compressorsection, to receive air compressed by low pressure compressor 44 andhigh pressure compressor 52. Mid-turbine frame 57 includes airfoils 59which are in the core airflow path. Turbines 46 and 54 are in fluidcommunication with combustor 56, wherein the expanding gas provided bycombustor 56 drives the respective low speed spool 30 and high speedspool 32.

FIG. 2 is a perspective view of mid-turbine frame (MTF) 57 according toan embodiment of the present invention. MTF 57 includes outer frame case62, inner frame case 64, and a plurality of hollow spokes 65. Outerframe case 62 includes an outer diameter portion 66. Inner frame case 64includes an outer diameter portion 70 and inner diameter portion 72. Inthe embodiment shown in FIG. 2, six hollow spokes 65 are distributedevenly around the circumference of radial inner case 64 to providestructural support between inner frame case 64 and outer frame case 62.

Inner frame case 64 supports the rotor assembly via bearing assemblies38 (shown in FIG. 1), and distributes the force from inner frame case 64to outer frame case 62 via the plurality of hollow spokes 65. A numberof arrangements are possible for attaching hollow spokes 65 to innerframe case 64. In one embodiment, inner frame case includes a pluralityof apertures (not shown) for receiving each hollow spoke 65, and one ormore bolts for attaching each hollow spoke 65 to inner frame case 64.Attachment of hollow spokes 65 to outer frame case 62 is provided at aplurality of bosses 75 located circumferentially around outer diametersurface 66 of outer frame case 62. In one embodiment, attachment ofhollow spokes 65 at bosses 75 may be secured by a nut (not shown) thatallows hollow spokes 65 to be tensioned. Apertures 76 formed in each ofthe plurality of bosses 75 allows cooling air to be distributed into ahollow portion (shown in FIG. 3) of each hollow spoke 65. In this way,cooling airflow is directed from the outer diameter through the hollowportion of cooled spoke 65 towards inner frame case 64. A metering plate(not shown) may be employed to meter or control the flow of coolingairflow into cooled spoke 65. Depending on the application, the size ofthe metering plate may be adjusted to selectively increase or decreasethe volume of cooling air provided to hollow spokes 65. The volume ofcooling airflow provided dictates the amount of cooling provided tohollow spokes 65.

Each of the plurality of hollow spokes 65 is subject to a varyingtemperature gradient caused by the expanding hot gases provided fromhigh pressure turbine section 54 to low pressure turbine section 46(shown in FIG. 1). If unmitigated, the temperature difference betweeneach of the plurality of hollow spokes 65 results in a thermal growthdifferential between the plurality of spokes that affects the overallroundness of the engine relative to the centerline axis A (as shown inFIG. 1). The present invention utilizes hollow spokes that receivecooling airflow to mitigate the effects of the hot gas path. The coolingairflow creates a high heat transfer coefficient with the spoke ascompared to the heat transfer coefficient outside of the spoke. Theresulting difference in heat transfer coefficients results in thecooling airflow within each hollow spoke 65 being the dominant factor inthe temperature of spokes 65.

FIG. 3 is a cross-sectional view of mid-turbine frame (MTF) taken alongline 3-3 of FIG. 4. FIG. 3 illustrates with respect to each cooled spoke65 a hollow portion 80 that extends from a first end of cooled spoke 65attached to the outer frame case 62 to a second end of cooled spoke 65attached to the inner frame case 64. The cross-sectional view providedin FIG. 3 also illustrates manifold 78 provided within inner frame case64 for receiving cooling air from each of the plurality of cooled spokes65 as indicated by the direction of the arrows through hollow portion 80of each cooled spoke 65. Manifold 78 is defined as the space betweenouter diameter portion 70 and inner diameter portion 72 of inner framecase 64, and between radial surface 82 and an opposing radial surface(not visible in this view) also of inner frame case 64. Cooling airflowis provided to manifold 78, which combines the cooling airflow from eachof the plurality of hollow spokes 65. In one embodiment, airflowprovided to manifold 78 is subsequently directed to cool a rotor portionlocated adjacent to manifold 78.

FIG. 4 is a cross-sectional view of mid-turbine frame (MTF) 57 takenalong line 4-4 of FIG. 2 that illustrates the geometry of manifold 78.In particular, manifold 78 is defined by radial portions 82 and 86,outer diameter portion 70 and an inner diameter portion 72 (not visiblein this view). Cooling airflow provided via cooled spokes 65 flows intomanifold 78 as indicated by the direction of the plurality of arrowsthrough hollow portions 80 of each cooled spoke 65. The presentinvention therefore compensates for temperature gradients in themid-turbine frame of a gas turbine engine through utilization of hollowspokes for communicating load forces between an inner frame case and anouter frame case, while being cooled via cooling airflow providedthrough the hollow portion of each spoke.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Forexample, although depicted as a turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with turbofans as theteachings may be applied to other types of turbine engines includingthree-spool architectures. In addition, many modifications may be madeto adapt a particular situation or material to the teachings of theinvention without departing from the essential scope thereof. Therefore,it is intended that the invention not be limited to the particularembodiment(s) disclosed, but that the invention will include allembodiments falling within the scope of the appended claims.

The invention claimed is:
 1. A turbine engine comprising: a combustor; a first spool comprising a high pressure compressor connected to a high pressure turbine; a second spool comprising a low pressure compressor connected to a low pressure turbine; and a mid-turbine frame located axially between the high pressure turbine and the low pressure turbine, the mid-turbine frame having an outer frame case connected to an inner frame case via a plurality of cooled spokes, wherein each of the plurality of cooled spokes has a radially outer end and a radially inner end and is hollow within a spoke wall for supplying cooling airflow from outside the outer frame case to the inner frame case, wherein the inner frame case includes a manifold defined by an outer diameter annular portion, an inner diameter annular portion, first and second radial portions of the inner frame case that extend radially between the outer diameter annular portion and the inner diameter annular portion, and wherein a radially inner end of the spoke wall of each of the plurality of cooled spokes meets the outer diameter annular portion of the manifold at an opening in the outer diameter annular portion extending from a radially outer surface of the outer diameter annular portion and a radially inner surface of the outer diameter annular portion, and terminates between the radially outer surface of the outer diameter annular portion and the radially inner surface of the outer diameter annular portion to define an airflow path from each of the plurality of cooled spokes into the manifold that allows the manifold to receive and combine the cooling airflow from the plurality of cooled spokes.
 2. The turbine engine of claim 1, wherein the mid-turbine frame includes three or more of the plurality of cooled spokes evenly distributed around the inner frame case.
 3. The turbine engine of claim 1, wherein the outer frame case includes a plurality of bosses located on an outer surface of the outer frame case for attachment to each of the plurality of cooled spokes.
 4. The turbine engine of claim 1, wherein the second spool further comprises: a gearbox connected to at least one of the low pressure compressor and low pressure turbine; and a fan connected to the gearbox.
 5. A mid-turbine frame located in a gas turbine engine axially aft of a high pressure turbine and fore of a low pressure turbine, the mid-turbine frame comprising: an outer frame case; an inner frame case; and a plurality of hollow spokes each having a spoke wall with a radially outer end and a radially inner end, the spoke wall being attached between the outer frame case and the inner frame case to distribute force from the inner frame case to the outer frame case, wherein each of the plurality of hollow spokes is configured to receive a cooling airflow therethrough; wherein the inner frame case includes a manifold defined by an outer diameter annular wall, an inner diameter annular wall, and first and second axial walls of the inner frame case that extend radially between the outer diameter annular wall and the inner diameter annular wall; and wherein a radially inner end of the spoke wall of each of the plurality of hollow spokes meets the outer diameter annular wall of the manifold at an opening in the outer diameter annular wall of the manifold and terminates radially between a radially outer surface of the outer diameter annular wall and a radially inner surface of the outer diameter annular wall to define an airflow path from each of the plurality of hollow spokes into the manifold that allows the manifold to receive and combine the cooling airflow provided via the plurality of hollow spokes.
 6. The mid-turbine frame of claim 5, wherein the mid-turbine frame includes three or more of the plurality of hollow spokes evenly distributed around the inner frame case.
 7. The mid-turbine frame of claim 5, wherein the outer frame case includes a plurality of bosses located on an outer surface of the outer frame case for attachment to each of the plurality of hollow spokes.
 8. The mid-turbine frame of claim 5, wherein the high pressure turbine is connected to a high pressure compressor.
 9. The mid-turbine frame of claim 5, wherein the low pressure turbine is connected to a low pressure compressor.
 10. The mid-turbine frame of claim 9, wherein the low pressure turbine is connected to a fan through a gearbox. 